Function enhancing method of T cell

The present invention features method for enhancing T cells, characterized by inhibiting the expression of Programmed Death-1 Ligand 1 T cell (PD-L1) and / or Programmed Death-1 1igand 2 (PD-L2), said to therapeutic agents comprising a performance enhancing T cell and the performance enhancing T cell obtained by the function enhancement method. The T cells, enhance the immune response to cancer, effective cancer immunotherapy, it is useful in the treatment or prevention of infectious diseases and autoimmune diseases.